1. Field of the Invention
An aspect of the invention relates to an inclination adjusting device for adjusting an inclination of a light controlling element used in optical scanners including those incorporated in laser printers.
2. Description of the Prior Art
There have been provided laser printers comprising an optical scanner, for example, in which a photosensitive member is horizontally scanned by light beams emitted from a light source, so that an image to be recorded is formed on the photosensitive member as a set of dots. In such an optical scanner, a single light beam is generally used to scan the photosensitive member. For improvement in a recording speed, the prior art has provided optical scanners of the multibeam type in which a multiple of light beams concurrently scan the photosensitive member.
FIG. 33 illustrates one of the conventional optical scanners of the multibeam type. Four light beams concurrently scan the photosensitive member in the shown optical scanner. More specifically, light beams emitted from four semiconductor lasers are collimated by collimator lenses 2 respectively. The collimated beams are reflected on mirrors 3 serving as light controlling elements respectively. The beams reflected on the respective mirrors 3 are further reflected on a galvanometer mirror 4 and then focused by a focusing lens 5, thereby being thrown onto a photosensitive member 6 as light beam spot. The photosensitive member 6 is moved in a direction crossing a scanning direction or in a direction of arrow X in FIG. 33. Consequently, an electrostatic latent image corresponding to image information is formed as a set of dots on the photosensitive member 6.
In the above-described optical scanner, the light beam spots of the four light beams need to be focused on the photosensitive member 6 so as to be arranged at predetermined intervals vertically with respect to the scanning direction. This requires adjustment in an inclination of the mirror 3 for adjustment of the direction in which the light beams are reflected.
One conventional inclination adjusting device for adjusting the inclination of the mirror includes a stepping motor as a driving source. The inclination adjusting device comprises an output shaft of the stepping motor and a gear reduction mechanism including a worm and worm gear. A driving force of the stepping motor is transmitted via the gear reduction mechanism to the mirror. The number of pulses supplied to the stepping motor or a rotational speed of the stepping motor and a direction of rotation thereof are controlled so that the inclination of the mirror is adjusted.
In the above-described inclination adjusting device, a resolution of rotational angle of the mirror can be improved since the output of the stepping motor is transmitted via the gear reduction mechanism to the mirror. Consequently, the inclination of the mirror can be fine-adjusted with high accuracy. However, the gear reduction mechanism including the worm and worm gear complicates the structure of the inclination control device and increases its manufacturing cost. Furthermore, a large-sized device results in a problem of dispositional limitation relative to the other parts of the photosensitive scanner. Additionally, a backlash unavoidably occurs between the worm and worm gear in the above-described gear reduction mechanism. The backlash shakes the mirror, resulting in a reduction in the accuracy of the adjusted inclination.
U.S. Pat. No. 5,610,752 to Hayakawa discloses another inclination adjusting device. As shown in FIG. 34, the device comprises a mirror 3 fixed to a magnet 8 rotatably mounted on a holder 7. A yoke 10 including a coil 9 and a magnetic member is provided around the magnet 8. In an initial state, that is, when the coil 9 is deenergized, an attractive force between the magnet 8 and the yoke 10 locates the mirror 3 so that the mirror crosses the sides of the yoke 10. Upon energization of the coil 9, a magnetic field induced in the coil rotates the magnet 8. Accordingly, the energization of the coil 9 is controlled for adjustment of the direction, magnitude, etc. of the magnetic field, so that the inclination of the mirror 3 is adjusted.
In the above-described device, however, the mirror 3 is surrounded by the coil 9 and the yoke 10. This construction results in an increase in the size of the device. Furthermore, the mirror 3 returns to its initial position when the coil 9 is deenergized. The coil 9 needs to be continuously energized so that the mirror 3 is held in a predetermined inclination. Moreover, the magnet 8 is allowed to be rotated even while the coil 9 is energized. For example, when the device is subjected to an external force such as vibration, rotation of the magnet 8 changes the inclination of the mirror 3.
Aspects of the present invention relate generally to inclination adjustment for light control as used in optical scanning devices.
The invention also provides an inclination adjusting device comprising an ultrasonic motor including a stator provided with a piezoelectric element and a rotor rotated by a traveling wave generated in the stator, and a light controlling element provided on the rotor so that an inclination thereof is adjusted according to rotation of the rotor.
The ultrasonic motor can accurately adjust the inclination of the light controlling element since it has a high resolution of rotor rotation angle. Furthermore, the inclination of the light controlling element is adjusted according to the rotation of the rotor without the conventionally used gear reduction mechanism. The construction of the inclination adjusting device can be simplified and the size thereof can be reduced.
In the ultrasonic motor, the traveling wave is generated in the stator while the latter is pressed against the rotor, so that a frictional force between the stator and the rotor causes the rotor to rotate. In view of this, the device further comprises a rotor presser for pressing the rotor against the stator or stator presser for pressing the stator against the rotor. In this construction, a large frictional force can be obtained without slippage and backlash in the rotor and/or stator. Consequently, the accuracy in the adjustment of inclination of the light control element can be improved.
The inclination adjusting device further comprises a rotational shaft provided on the rotor, a pedestal having a concavity in which the rotational shaft is rotatably mounted, and a shaft presser for pressing the rotational shaft against the pedestal. Since the rotor is rotated without slippage and backlash in this construction, the accuracy in the adjustment of inclination of the light controlling element can improved.
The inclination adjusting device further comprises a rotor support for supporting the rotor and a stator mount on which the stator is mounted. The rotor support and the stator mount are discrete from each other. In this construction, the location of the stator mount is adjusted relative to the rotor support so that the stator is positioned relative to the rotor. Consequently, the stator and the rotor can be positioned readily and reliably.
The light controlling element comprises a mirror, a half mirror, a prism, or a dichroic mirror. In the prism, three sides thereof serve as light transmitting or reflecting faces. In such a case, the inclination adjusting device further comprises a pivot shaft. The prism has one of opposite ends connected to the rotor and the other end supported on the pivot shaft. Furthermore, the device further comprises a pivot shaft support for supporting the pivot shaft for an axial movement and pivot shaft presser for pressing the pivot shaft against the prism. The pivot shaft or the prism can be prevented from backlash.
The inclination adjusting device further comprises a motor mount on which the ultrasonic motor is mounted, a holder provided on the motor mount for rockably holding the light controlling element, an abutting member abutting a portion of the light controlling element spaced away from a center of rocking motion, the abutting member being displaced by rotation of the rotor. In this construction, the abutting member is displaced so that an inclination of the light controlling element is adjusted.
According to the above-described construction, rotation of the rotor displaces the abutting member, so that the inclination of the light controlling element is varied. An amount of variation in the inclination of the element relative to an amount of rotation of the rotor is rendered smaller in this construction than in the construction in which the light controlling element is provided on the rotor such that an amount of rotation of the rotor is equal to an amount of variation in the inclination of the light controlling element. Consequently, the accuracy in the adjustment of the inclination of the light controlling element can further be improved. Furthermore, the motor is energized when the abutting member is displaced. However, the motor need not be energized to maintain the inclination of the light controlling element. Consequently, an electric power saving can be achieved.
The holder preferably includes a supporter for supporting the light controlling element and light controlling element presser for pressing the light controlling element against the abutting member. The light controlling element is usually pressed against the abutting member by the light controlling element presser. Consequently, the inclination of the light controlling element can be prevented from being changed by an external force applied to the device.
The invention further provides an inclination adjusting device comprising a mount, a controlled member, a holder provided on the mount for rockably holding the controlled member, an abutting member abutting a portion of the controlled member spaced away from a center of rocking motion, and a displacer provided on the mount for displacing the abutting member so that an inclination of the controlled member is adjusted.
The displacer may comprise a rotary actuator or a linear actuator.
Another embodiment of the present invention includes an optical scanner comprising a light emitting element, which emits a light beam, an inclination adjusting element and a scanning element. The inclination adjusting element includes a light controlling element, which adjusts an optical path of the light beam emitted by the light emitting element, a mount, and a holding member provided on the mount for rockably holding the light controlling element. In addition, the inclination adjusting element also includes an abutting member abutting a portion of the light controlling element spaced away from a center of rocking motion, a pressing element, which presses the light controlling element against the abutting member, and an actuator provided on the mount. The actuator is provided for displacing the abutting member in abutment with the light controlling element so that a distance between the portion of the light controlling element abutted against the abutting member and the center of rocking motion is varied.
Another embodiment of the present invention includes an inclination adjusting device for a light controlling element. In this embodiment, the inclination adjusting device comprises a light controlling element, a mount, a holding member, an abutting member, a pressing element, and an actuator. The holding member is provided on the mount for rockably holding the light controlling element, and the abutting member is provided for abutting a portion of the light controlling element spaced away from a center of rocking motion. The pressing element presses the light controlling element against the abutting member. The actuator is provided on the mount for displacing the abutting member in abutment with the light controlling element so that a distance between the portion of the light controlling element abutted against the abutting member and the center of rocking motion is varied. Through this variance, the inclination of the light controlling element is adjusted.